1. Field
Example embodiments relate to an extreme ultraviolet (EUV) projection lens and an, optic system having the same. More particularly, example embodiments relate to an EUV projection lens having a high transmittance and an optic system having the same.
2. Description of the Related Art
As semiconductor devices have been highly integrated, forming more complex and fine patterns on a wafer becomes more important. Recently, an extreme ultraviolet (EUV) light source has been studied instead of a krypton fluoride (KrF) light source having a wavelength of 248 nm or an argon fluoride (ArF) light source having a wavelength of 193 nm in an exposure process because resolution may be increased by using a light source having a smaller wavelength. In an EUV lithography process, an EUV light source having a wavelength in a range of 13 nm to 14 nm may be used, and a photomask that may be used in the EUV lithography process needs to be developed. A various optic system using the EUV light source is also needed so that each pattern of the photomask may be inspected.
However, EUV light may have a very low transmittance and a high absorptance, and thus a visible light projection lens may not be used for the above optic system. Accordingly, an optic system using EUV light may use a mirror coated with multilayers reflecting EUV light as a condensing lens.
The reflection mirror may have a complex multilayered structure so that the mirror may have low surface quality and be expensive. Further, the aberration and alignment of the mirror may not be optimized. Thus, an EUV projection lens that is cheap and usable for an optic system using EUV light is required.